Manufacture of stabilized silver halide emulsions



Patented Oct. 20, 1936 UNITED STATES PATENT OFFICE MANUFACTURE OFSTABILIZED SILVER HALIDE EMULSIONS No Drawing. Application July 19,1934, Serial 16 Claims.

My present invention relates to stabilizing 10 on a photographic silverhalide emulsion which may be unsensitized or which has been sensitizedor hyper-sensitized increases the stability of this emulsion.

As compared with the known stabilizers the sull phinates and theselninates have the advantage of not affecting thephotographicproperties of the emulsion, for example the sensitivity and gradation.

For the purpose of the invention there may be 20 used an alkali salt oranother soluble salt of an aliphatic or aromatic or hydroaromatic orheterocyclic sulphinicor seleninic-acid, for instance, such a salt ofmethane-sulphinic acid, methane disulphinic acid, methane-trisulphinicacid, 25 ethane-sulphinic acid, ethane disulphinic acid,benzene-sulphinic acid, a chlorobenzene-sulphinic acid,toluene-para-sulphinic acid, anisol-parasulphinic acid,acetanilide-para-sulphinic acid, salicylic-sulphinic acid,benzene-meta-disulphinic o acid, naphthalene-p-sulphinic acid,cyclohexylsulphinic acid, thiophene-sulphinie acid, benzeneseleninicacid, methane-seleninic acid, ethaneseleninic acid.

Instead of the salts, the free acids likewise may 35 be used. However,if the quantity used is too large, a loss of sensitivity occurs as aconsequence of the reduction of the pH-value. Therefore, the stabilizeris preferably added in the form of a salt. The amount of stabilizeradded to 1 kg. of wet at, emulsion generally varies from 0.5 to 5 grams.

However, the invention is not limited to these quantities; the mostsuitable amount of stabilizer to be used can be easily determined byexperi- 50 is used a liquid in which the stabilizer is soluble i a andwhich does not affect the emulsion. Preferably there is used water or anorganic solvent which is miscible with water, for instance, alcohol. Ihave furthermore found, that the fogging infiuence of supports,preparation layers, backing benzene-seleninic acid in 25 cc. of water.

In Germany July 22, 1933 layers, intermediate layers, sub-layers,protective layers, or baryta-layers can be prevented by incorporating inthese layers the salt of a sulphinic or seleninic acid. For instance, ananti-halation layer of glassmakers soap often causes fogging 5 of thesilver halide. emulsion layer to which it is attached, so that suchphotographic materials have a poor stability. Furthermore the paper usedfor finishing or packing photographic materials causes the emulsion tobe fogged and thus shortens the life of the photographic material. Thefogging action of the aforesaid materials can be considerably reduced bythe incorporation of a salt of a sulphinic acid or a seleninic acid.

The following examples serve to illustrate the invention.

Example 1.l kilo of a wet gelatino silver halide emulsion containing 6to 7 per cent of silver halide and 8.5 per cent of gelatin is molten inthe usualway and mixed with a solution of 3 grams of the sodium salt ofbenzene-sulphinic acid in cc. of Water. The emulsion is then cast on afilm base and made partly into a roll film and partly into a film pack.These films and films made with the same silver halide emulsion, butwithout 25 the addition of the sodium salt of benzene-sulphinic acid,showed when freshly prepared the same sensitivity and the same fog of0.12 density unit. After storing the roll film in a drying stove heatedto 50 C. for two weeks the film showed a fog of:

Density unit Film without addition 0.43 Film with the sodium salt ofbenzene-sulphinic acid- 0.25

After storing the film packs in a drying stove heated to 50 C. for threeweeks, the films showed a fog:

Density unit Film without addition 0.55to0.60 Film containing the sodiumsalt of benzene-sulphinic acid 0.25 to 0.28

Similar results are obtained when the sodium salt of benzene sulfinicacid is replaced'by the sodium salt of ethane sulfinicacid, achlorobenzene-sulfinic acid, toluene-para-sulfinic acid, ornaphthalene-sulfinic acid,

Ewamplc 2:1 kilo of an unsensitized wet emulsion containing 9 per centof gelatin and 6 to 7 per cent of silver halide is molten and mixed witha solution of 1 gram of the sodium salt of The emulsion is then cast onglass plates. In freshly prepared condition the plates made from theDensity unit Emulsion without addition 0.43 Emulsion containing thesodium salt of benzene-seleninic acid -1 0.21

Example 3:-An Agfa-Isochrome" plate (registered trade-mark) is bathedfor 10 minutes in the following solution:

Water liter" 1 Crystalline sodium carbonate grams 5 Concentrated ammoniasolution cc 5 Sodium salt of hexahydrobenzene-sulfinic a i grams 10After having been thoroughly rinsed the plate is dried in a current ofwarm air. The plate is stored in a drying stove heated to C. for threedays together with a plate of the same brand of emulsion which has notbeen bathed. After this treatment the plates showed a fog:

Density unit Plate containing the sodium salt ofhexahydrobenzene-sulflnic acid 1.3

Example 4.'To 1 kilo of an emulsion of glassmakers soap in gelatincontaining about 8 per cent of gelatin there is added a solution of 5grams of the sodium salt of ethane-suifinic acid in 25 cc. of water, andthe emulsion is cast on a support to form an anti-halation layer. On thedry anti-halation layer there is cast a photographic emulsion containing6 to 7 per cent of silver halide and 8.5 per cent of gelatin andsensitized with 1.1'-diethyl-6-methyl-benzthiopseudocyanine iodide or1.1'-diethyl-benzselenopseudocyanine perchlorate. (The emulsion containsabout 15 m r. of sensitizer in 1 kilo of wet emulsion.) The photographicmaterial thus made was stored in a drying stove heated to 50 C. to-

gether with photographic material made in the same manner but withoutthe addition of the sodium salt of ethane-suifinic acid. After 9 daysstoring the materials showed a fog:

Density unit Material without addition 0.94

Material with addition of the sodium salt of 1 ethane suifinic acid.0.48

Example 5:Black-red paper such as is used in winding roll films isbathed for 10 minutes in a 10 per cent solution of the sodium salt ofthiophene-sulflnic acid in methanol of 50 per cent strength. This paper,as well as paper which has been treated with methanol of 50 per centstrength without addition and paper which has not been treated at allwere placed in contact with the emulsion side of a photographic film ina drying stove heated to 50 C. The film showed a fog of 0.08 densityunit before beginning the test. After a 9 days storing the films showeda fog:

The test in the above examples was performed by developing thephotographic emulsion tor 5 minutes'in a developer of the-following composition:

Water was- -1 Para-methylaminophenol sulfate -grams-.. 1.5 Hydroquinone-do 2.5 Potassium carbonate do 18.0 Potassium bromide do---.. 1.0 Sodiumsuliite sicc -do 18.0

The film was then fixed, and after drying the density was determined inthe Martens densitometer.

In the examples gelatin is used as a binding agent for the emulsion,however, the stabilizing eflect of the described stabilizers is notlimited to emulsions prepared with this binding agent, but there may beused also other binding agents, for instance, collodium, agar-agar,casein, albumen, and polyglucuronic acid.

As above described the stabilizer may be added to the emulsion at anystage of its production, but it may also be added already to the parentmaterial for making the emulsions. When the stabilizing agent is to beadded to the support to which the emulsion is attached, it is preferablyadded before the support is cast. To a preparation layer, anintermediate layer, a backing, a sub-layer or a protective layer thestabilizer is added shortly before casting these layers. In the case ofpaper it is preferably added to the paper pulp. In the case of papercoated with gelatin and barium sulfate it is added to the castingsolution from which the layer is made.

What I claim is:

1. A method of preventing a silver halide emulsion from becoming foggedwhich comprises bring the emulsion in contact with a soluble compoundselected from the group consisting of a sultlnic acid, a seleninic acidand their salts.

2. A method of preventing a silver halide emulsion from becoming foggedwhich comprises bringing the emulsion in contact with a soluble salt ofan acid selected from the group consisting of a suifinic acid and aseleninic acid.

3. A method of preventing a silver halide emulsion from becoming foggedwhich comprises bringing the emulsion in contact with an alkali salt ofan acid selected from the group consisting of a suifinic acid and aseleninic acid.

4. A method of preventing a silver halide emulsion from becoming foggedwhich comprises incorporating in a layer which is in contact with theemulsion layer a soluble salt of an'acid selected from the groupconsisting of suifinic acid and seleninic acid.

5. A method of preventing a silver halide emulsion from becoming foggedwhich comprises incorporating in the emulsion a soluble salt of an acidselected from the group consisting of sulfinic acid and seleninic acid.

6. A method of preventing a silver halide emulsion from becoming foggedwhich comprises adding to a wet and molten gelatino silver halideemulsion sodium salt of benzene-suifinic acid dissolved in 25 cc. ofwater and casting the photographic material from this emulsion.

7. A method of preventing a silver halide emulsion from becoming foggedwhich comprises adding to a wet emulsion of gelatin and glassmakers soapsodium salt of ethane-sulfinic acid dissolved in 25 cc. of water,casting the emulsion on a support to form an anti-halation layer, dryingthis layer, and casting on this layer a gelatino silver halide emulsioncontaining a sensitizer.v

8. A method or preventing a silver halide emulsion irom becoming loggedwhich comprises adding to a wet gelatino silver halide emulsion so diumsalt of benzene-seleninic acid dissolved.- in 25 cc. of water andcasting the emulsion from this solution.

9.- A photographic material comprising a silver halide gelatin emulsionin contact with a soluble compound selected from the group consisting ofa sulflnic acid, a seleninic acid and their salts.

10. A photographic material comprising a silver halide emulsion incontact with a soluble salt of an acid selected 'from the groupconsisting of a sulflnic acid and a seleninic acid.

11. A photographic material comprising a silver halide emulsion incontact with an alkali salt of an acid selected from the groupconsisting of a sulflnic acid and a seleninic acid.

12. A photographic material comprising a silver halide emulsioncontaining as an addition a soluble salt of an acid selected from thegroup consisting of a sulflnic acid and a seleninic acid.

13. A photographic material comprising a gelatino silver halide emulsionin contact with a layer containing a soluble salt of an acid selectedfrom the group consisting of a sulflnic acid and a seleninic acid.

14. A photographic material comprising a silver halide emulsioncontaining the sodium salt of benzene-sulflnic acid.

15. A photographic material comprising a gelatino silver halide emulsioncontaining the sodium salt of benzene-seleninic acid.

' 16. A photographic material comprising a support, attached to saidsupport an anti-halation layer comprising gelatin as a binding agent andhaving incorporated glassmakers soap and the sodium salt ofethane-disulflnic acid, and attached to this anti-halation layer agelatino silver halide emulsion layer containing a sensitizer.

JOHANNES BRUNKEN.

